MetaLS-like virtual text evaluation instead of comments

## Is your enhancement request related to a problem? Please describe.

I find the choice of having evaluation (`-- >>>`) result as comments suboptimal, since I would like the result to be only shown to the reader of the code and not be a textual part of the document. This is not a blocker, but it can be better.

## Describe the solution you'd like
Scala's MetaLS[^1] supports a special file type: "worksheets". For this kind of files, every expression is evaluated on-the-fly and the value of that line is shown as virtual text on the side.

It is worth considering evaluating each (pure) expression and have their value on the right-hand side. It can be an interesting feature, documenting examples for beginners. However, the focus of my suggestion remains on using virtual text over comments.

I have previously opened an issue here mrcjkb/haskell-tools.nvim#258

## Describe alternatives you've considered
`ghci`, but it's nowhere as immersive and intuitive as having inline evaluation on the fly.

## Additional context
Maybe long lines will be truncated (at least, I do not know how to avoid it). I might do some research on this when I have free time.

Thank you for the project and for reading my suggestion :)

[^1]: [Meta Language Server](https://github.com/scalameta/nvim-metals)